Abbott, Ben N.¹, Stanley T. Paxton¹, Robert W. Puls², Jamie L. Schlottmann³
(1) Oklahoma State University, Stillwater, OK
(2) USEPA, Ada, OK
(3) Consultant, Edmond, OK

ABSTRACT: Subsurface Well-Log Correlation of Arsenic-Bearing Lithofacies in the Permian Garber Sandstone and Wellington Formation, Central Oklahoma Aquifer (COA), Cleveland County, Oklahoma

The Garber-Wellington aquifer is an important source of drinking water in central Oklahoma. The formations making up the aquifer, the Garber Sandstone and the underlying Wellington Formation, consist of amalgamated fluvial sandstones interbedded with mudstones, siltstones, and some conglomerates (Breit et al., 1990). Water from some of the wells contains naturally occurring arsenic levels that exceed federal standards (EPA, 2001). Past work suggests that the arsenic is concentrated in water produced from sandstones isolated by finer-grained rocks. This is because the low permeability of the finer-grained intervals inhibits the flushing-out of soluble trace substances by freshwater (Schlottmann et al., 1998). Therefore, one strategy for remediation is to selectively produce water from low-arsenic zones and to limit or avoid completion and development of sandstones isolated by finer-grained lithofacies. This strategy requires the development of an improved stratigraphic model that defines the lateral and vertical distribution of arsenic-prone lithofacies. To accomplish this, geophysical logs from oil and water wells, subsurface core, and outcrops are being used to produce stratigraphic cross-sections and maps (such as net-to-gross and sandstone-shale ratio maps). To date, our work suggests that sand-prone and mud-prone packages within these formations can be correlated but that correlation of individual sandstone bodies is problematic. Through integration of on-going companion studies, the projection of outcrop gamma-ray profiles and paleodepositional environment to the subsurface should help to further constrain the habitat of arsenic and better define regional permeability fairways. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.)

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.